1. Field of the Invention
The present invention relates to inductor devices formed by a spiral conductor.
2. Description of the Related Art
Conventionally, in a semiconductor integrated circuit, a spiral conductor is formed on a substrate by using a thin-film deposition technique, for example, and such a spiral conductor is used as an inductor device. It is required for the inductor device to operate stably even if a high-frequency signal flows through the inductor device. In order to fulfill such a requirement, it is necessary to increase inductance of the inductor device. Generally, the inductance of an inductor device is increased proportional to the number of times a conductor is wound around.
When the number of turns of a spiral conductor is increased, however, the area of a substrate occupied by the inductor device (spiral conductor) is increased. Hence, conventionally, spiral conductors are formed in two stages and connected to each other so as to increase the inductance while avoiding an increase in the area of the substrate occupied by the inductor devices (spiral conductors) (refer to Japanese Laid-Open Patent Application No. 3-89548, for example).
However, the inductor device, which is disclosed in Japanese Laid-Open Patent Application No. 3-89548 and formed in two stages, has a so-called peripheral shape, and an external connection terminal is formed at an outer peripheral end of the inductor device (spiral conductor). Hence, it is necessary to provide a region for forming the external connection terminal in the periphery of a region where the spiral conductor is formed, which prevents further integration.